A senate is a deliberative body, often the upper body of a legislature.
A deliberative body of faculty in an institution of higher learning is often called a senate.

The original senate was the Roman Senate.
The word senate is derived from the Latin word senex (old man), via the Latin word senatus (senate).
Its meaning comes from a very ancient form of even simple social organisation in which the decisional power is reserved to the eldest men.
For the same reason, the word senate is correctly used when referring to any powerful authority characteristically composed by the eldest members of a community, as above mentioned Academic Senates.

Modern democratic states with parliamentary representatives are sometimes organised with a Senate, often distinguished by an ordinary parallel Chamber of Deputies (in bicameral systems) by electoral rules (minimum age required for voters and candidates, proportional or majority system, electoral basis = collegium).
Typically, the senate is referred to as the upper house, and has a smaller membership than the lower house.

An example of this is the United States Senate where the number of seats is fixed at two per state, regardless of size.
In a federal system, the senate often serves a balancing effect by giving a larger share of power to regions and groups which would otherwise be overwhelmed in a purely representative system.
In United States state legislatures, Senates were used for this purpose until the 1963 Baker v. Carr, in which the Supreme Court of the United States ruled that state legislatures must apportion seats according to population.

In the United States, each of its member states has a Senate and a variously-named second chamber, except for the state of Nebraska, where the Senate is the only body of a unicameral legislature.